Indene has been used in the preparation of synthetic resins for many years, e.g., coumarone-indene or coal-tar resins in which coumarone is only a small component. The commercial importance of these resins has diminished over the past decade. More recently indene has found use as a comonomer in other resins and, in high purity, as a monomer to improve the surface properties of polymers with minimal loss to vaporization due to its low vapor pressure.
Polymerization of indene and/or derivatives of indene provides valuable precursors for the formation of synthetic carbon fibers. Their use can improve carbon fiber processing and properties. As disclosed in U.S. Pat. No. 4,091,196 to Smith et al., production of a carbon fiber precursor for use in relatively sophisticated applications requires stringent control over process variables and raw materials. It will be seen that in such applications a method by which control over monomer quality may be reproducibly achieved would be advantageous.
By way of general background, McArthur, in U.S. Pat. Nos. 3,856,702, 3,856,705 and 4,024,171, discloses that it has long been the practice in the art to impregnate or otherwise distribute active catalytic metals upon support materials having desired properties of porosity, surface area, thermal and mechanical stability, and suitably inert chemical properties. In U.S. Pat. No. 4,024,171 McArthur discloses the use of catalysts comprising an aluminum borate support post treated with copper. Among the reactions disclosed for this catalyst are dehydrocyclization of C.sub.6+ paraffins to produce corresponding aromatic hydrocarbons. However, McArthur does not disclose crystalline copper aluminum borate having the unique X-ray diffraction pattern which is characteristic of the catalyst used in the present invention.
Commonly assigned U.S. Pat. No. 4,590,324 to Satek discloses dehydrogenation of alkylaromatics containing at least two carbons in at least one alkyl group to alkenylaromatics using a catalyst comprising metallic copper on a support comprising aluminum borate. More particularly, U.S. Pat. No. 4,590,324 discloses the dehydrogenation of ethylbenzene to styrene, cumene to alphamethylstryrene and paraethyltoluene to paramethylstryene (vinyltoluene) with the catalyst. The patent does not disclose or suggest use of the catalyst for dehydrocyclization of a polysubstituted cyclic compound forming a dehydrocyclization product comprising a polynuclear compound wherein the new ring comprises at least 5 carbon atoms.
Commonly assigned U.S. Pat. No. 4,740,647 to Hussman and McMahon discloses cyclization of aliphatic moieties of 3-20 carbons using copper aluminum borate catalyst, including aliphatic moiety attached to an aromatic nucleus provided that the starting compound has an unsubstituted ring carbon ortho to the ring carbon bonded to the aliphatic moiety. In particular, 5-(ortho-tolyl)pentene can be dehydrocyclized to mixtures of 1,5-, 1,6-, and 2,6-dimethylnaphthalene. The patent, however, does not disclose or suggest use of the catalyst for dehydrocyclization of a polysubstituted cyclic compound to effect cyclization between (i) a carbon atom of a first hydrocarbon radical and (ii) a carbon atom of a second hydrocarbon radical wherein the hydrocarbon radicals are bonded to adjacent ring carbons on the starting cyclic compound.
Recently, U.S. Pat. No. 4,891,462 dated Jan. 2, 1990, in the name of McMahon, which is a continuation-in-part of commonly assigned U.S. Pat. No. 4,740,647 to Hussman and McMahon, discloses use of the catalyst for cyclization-dehydrogenation by contacting the catalyst with a polynuclear-fused ring aromatic compound having an ethyl group bonded to a ring carbon adjacent a bridging carbon to effect cyclization across the bridging carbon. This cyclization is between (a) the ethyl carbon furthest from the ring and (b) a second ring carbon located two carbons from the first ring carbon and separated therefrom by the bridging carbon as in the products acenaphthene and acenaphthylene from cyclization-dehydrogenation of 1-ethyl-naphthalene over copper aluminum borate. The application does not disclose or suggest use of the catalyst for dehydrocyclization of a polysubstituted cyclic compound to effect cyclization between (i) a carbon atom of a first hydrocarbon radical and (ii) a carbon atom of a second hydrocarbon radical wherein the hydrocarbon radicals are bonded to adjacent ring carbons on the starting cyclic compound.
Pedersen et al., in U.S. Pat. No. 4,613,711, discloses dehydrocyclization of certain alkylaromatics to indene or a substituted indene by contacting certain alkylaromatics in admixture with H.sub.2 S with a sulfided metal oxide catalyst selected from CoO, NiO, MoO.sub.3 and WO.sub.3 on 60-98 weight percent of an alumina support and having a surface area (BET method) less than 100 m.sup.2 /g. The patent does not disclose or suggest use of any catalyst comprising either copper or boron.
Accordingly, there is a need for an improved process for production of polynuclear organic compounds by synthesis from polysubstituted organic compounds. Before the present invention, methods for obtaining many polynuclear compounds included separation of a desired compound from coal tar, petrochemical, refinery mixtures and additional purification, e.g., previous methods for obtaining high-purity indene including centrifugation, distillation and crystallization or adsorptive separation of indene-rich naphtha-cracker pyrolysis oil.
It is therefore a general object of the present invention to provide an improved method for preparing polynuclear organic compounds from certain polysubstituted ring compounds and, in particular, to provide an economical and reproducible cyclization-dehydrogenation process for preparing fused ring organic compounds wherein the new ring is formed by cyclization between groups in an ortho position to each other on a starting ring compound.
An additional need exists for a convenient method of preparing polynuclear organic compounds by synthesis from polysubstituted organic compounds without unnecessary losses to cracking and other compounds which are not intermediates in the formation of the desired polynuclear compounds, e.g., cracking products, isomerization products, and tars.
It is a further object of the invention to provide an improved method for preparing indene and/or derivatives of indene from ortho-ethyltoluene and/or substituted ortho-ethyltoluene. Other objects appear hereinafter.
In the discussion that follows, reference is made to Temperature Programmed Reduction. As discussed in Zletz copending U.S. Pat. No. 4,729,979 and Satek U.S. Pat. No. 4,590,324 (hereby incorporated by reference), this test was carried out by placing 1.5.times.10.sup.-4 moles of copper aluminum borate in a 0.6 mm outside diameter vycor tube heated by an electric furnace. The tube was purged with helium or argon by heating to 300.degree. C. After cooling to ambient temperature, the gas feed to the vycor tube was switched to either 5% carbon monoxide in helium or 5% hydrogen in argon and the temperature was ramped to about 850.degree. C. at 8.degree. C./min. The temperature was controlled and ramped by a programmer equipped with a temperature controller. The change in gas composition of the effluent was detected with a thermal conductivity cell equipped with output to a strip-chart recorder. The carbon dioxide formed was removed from the effluent by a bed of Ascarite, and the water formed was removed by magnesium perchlorate. Unless otherwise stated, pore volume, surface area and average pore radius was determined by BET nitrogen adsorption (desorption test).